A mechanism for writing abstract data to a stream
A DataOutputStream is a mechanism for writing any abstract data to a stream, regardless of the type of the data. A stream is usually comprised of data to write to a local file, or data being transmitted to a remote server over a network protocol such as HTTP or FTP.
An DataOutputStream is abstract, and doesn't describe the type of data that is being written. Typically, if you are able to, you would implement one of the subclasses instead, such as FileOutputStream, which more appropriately describes the type of data being handled, and provides additional methods appropriate for that data type.
